Abrasive brake shoe



A ril 10, 1956 G. K. NEWELL. 2,741,340

ABRASIVE BRAKE SHOE Filed Sept. 15, 1954 INVENTOR, @801 eKN BY AT TORNEYUnited States Patent ABRASIVE BRAKE snon George K. Newell, Pitcairn,Pa., ass ignor to Westinghouse Air Brake Company, Wilmerding, Pa., acorporation of Pennsylvania Application September 15, 1954, Serial No.456,273.

2 Claims. (Cl. 188-256) This invention relates to improvements in brakeshoes and more particularly to the type adapted for use with wheels ofrailroad cars and the like.

In the railway brake art, considerable progress has been made indeveloping brake shoes of composition materials which not only providelonger shoe life but also cause a minimum of wear of the railway carwheel, both of which qualities are essential characteristics of goodbrake shoes. It has been found, however, that composition brake shoes ofnon-wheel-wearing material are unable to effect rapid and satisfactoryburnishing of the tread surface of the wheel, which surface is normallysomewhat pitted and scarred, especially in the case of new wheels, whichin addition to normal pits and scars also have tool marks; and becauseof such imperfections on the tread surface, the brake shoes will wear atan excessive rate until said surface has been burnished.

It has heretofore been proposed to provide a brake shoe comprisingsegmental blocks of iron or steel separated by recesses in which areaccommodated blocks of Carborundum, the thickness of these abrasiveblocks being substantially equal to the thickness of the metallicblocks. A brake shoe of this type, however, is not only relativelyexpensive to manufacture but excessive wear of the wheel results becausethe abrasive is effective during substantially the full life of thebrake shoe.

The principal object of this invention is therefore to provide animproved composition brake shoe embodying abrasive means adapted toburnish and condition the brake-shoe-engageable surface of a wheelduring only a limited period of use following initial installation.

Another object is to provide an improved composition brake shoe which isespecially adapted to burnish and condition new railway car wheels, itbeing common practice to install a new set of brake shoes when suchwheels are installed.

According to the foregoing objects, the improved brake shoe comprises arelatively thin portion or layer which comprises abrasive material andis preferably formed integrally with the non-abrasive. compositionmaterial, such as during molding of the brake shoe. This portion orlayer may define a part or all of the arcuate, wheelengaging surface ofthe improved brake shoe, when in a new or unused state, such that afterinitial installation such layer or portion will be progressively wornaway during successive contacts with the wheel until, at some timeshortly after the wheel has been properly conditioned or burnished, onlypure composition brake material will remain, for thereafter engaging thewheel and thus preventing undesired wear of the wheel.

Other objects and advantages will become apparent from the followingdescription of the invention and from the accompanying drawing, whereinFig. 1 is a side elevational view, partly in section, of a four-segmenttype brake shoe embodying the invention; and Fig. 2 is a sideelevational view, partly in section, of a two-segment type brake shoeshowing another embodiment of the invention.

2,741,340 Patented Apr. 10, 1955 ice Description As shown in Fig. 1 ofthe drawing, the improved brake shoe may, for sake of illustration,comprise the usual metallic, generally convex-concave backing plate 1 tothe concave surface of which is suitably secured, as by molding, a bodyZ comprising four segments each preferably formed integrally with acommon backing portion that is adjacent to and co-extensive with thebacking plate 1. These segments have, at the opposite sides thereof fromthe backing portion, respective surfaces 3, 4, 5, 6, for engaging thetread of a wheel that is to be braked; the surfaces 3 and 6 being thoseprovided on the outer segments, that is, those which are farthest fromeach other.

The backing plate 1 is provided with the usual U-shaped lug or eyelet 7,which is preferably formed integrally with said plate at the oppositeside thereof from the body 2 and centrally disposed adjacent the convexsurface of said plate; said eyelet being provided for accommodating theusual key (not shown) whereby the brake shoe is connected to the usualbrake head (not shown).

According to the first embodiment of the invention, the body 2 iscomposed solely of composition brake material except for portions orlayers, designated by the reference numerals '8, 9, in which arecontained abrasive material, such as silicon carbide particles, ofpreselected density for conditioning and burnishing the wheel as it isworn off or expended by frictional contact with the rotating wheelduring an application of brakes; said portions preferably being formedintegrally with body 2, as by molding, at the time said body is moldedto the backing plate 1, as hereinafter explained. The abrasive portions8, 9 are adjacent to, and in part define, the wheel-engaging surfaces 3,6, respectively; and said surfaces are preferably in arcuate alignmentwith the wheel-engaging surfaces 4, 5, such that when the improved brakeshoe is first installed for use, all of said surfaces 3, 4, 5, 6, willengage the wheel during the initial application of brakes. 1

A multiple-segment type body, such as the body 2, has been foundpreferable in tests because the surfaces 3, 4, 5, 6 are separated bycavities 1t), 11, 12 respectively, which cavities not only permitabrasive material to be thrown free of the Wheel after wear from thesurfaces 3, 6 but also impart greater flexibility to the brake shoe andfacilitate cooling of the brake shoe.

In use, the abrasive material of portions 8, 9, will burnish the wheeland in so doing will be worn olf or expended or become dislodged withoutaffecting the braking force applied to the wheel through the medium ofthe brake shoe. During successive applications of brakes, the wheel willgradually become conditioned and the portions 8, 9 will becomeprogressively reduced in thickness. The portions 8, 9 are thereforepreferably no thicker than necessary to assure proper conditioning of awheel, so that when the wheel has been properly conditioned, theabrasive material of said portions will have been completely expended,and only non-abrasive composition brake material will thereafter engagethe wheel for preventing undesired wear thereof during the remaininglife of the brake shoe. I have found that best results are obtained whenthe thickness of the abrasive portions 8, 9 is about /s" to A.

In the preferred embodiment of the invention, as shown in Fig. l of thedrawing, in which only the wheel-engaging surfaces 3, 6 of the brakeshoe contain abrasive material, the rate of expenditure of such abrasivematerial will be desirably retarded due to the long-wearingcharacteristics of the composition brake material of which theWheelengaging surfaces 4, 5 are composed. With the rate of expenditureof abrasive material thus limited to the rate at which the purecomposition brake material is worn from the surfaces 4, 5, the abrasivematerial of surfaces t 3, 6 will effect what might be compared to alight sanding of the wheel for preventing undue wear of the wheel duringconditioning. In other words, by so engaging the wheel, thewear-resistant surfaces .4, act in the nature of a stop for retardingand controlling the rate of wear of the abrasive surfaces 3, 6 whichlatter surfaces :might otherwise, under action of a heavy braking.force, cause undue wear of the'wheei.

According to the second embodiment of the invention, as shown in Fig. 2of the drawing, a body 13 may, for sake of illustration, comprisetwosegments which are separated by a cavity 14 and have portions'lS, 16that comprise abrasive material and are in part defined by arcuate,wheel-engaging surfaces 17, 18, respectively. All parts which areidentical With those shown in Fig. 1 of the drawing are designated bylike reference numerals. The structure, as thus shown in Fig. 2 of thedrawing, is especially adapted for usewith new wheels where more rapidburnishing and conditioning is desired in order to remove the usualridges and tool marks from such wheels. Brake shoes of this type couldbe conveniently installed when :a new wheel is installed, .it being thecommon practiee to-install a new set of brake shoes at such time.

It will be noted that the abrasive material of the portions 15, 16 willbecome expended at a more rapid rate and thus more rapidly grind theridges and tool marks ofi thetread surface of the new wheel, than willoccur. with the type of brake shoe shown in Fig. 1 of the drawing andheretofore described. These abrasive portions 15, .16 are thereforepreferably only thick enough to accomplish the desired conditioning of anew wheel, so that by the time the wheel has become reconditioned, theabrasive be readily manufactured at practically no increase in cost overthose presently made. For sake of illustration, a mixture of abrasivematerial and composition brake material, previously prepared into abatch, could be spread at the bottom of the mold, either in the outersegments only or in all "segments, according to whether the .first orsecond embodiment of the invention is to be practiced; and thencomposition brake material devoid of abrasive material would be used tofill the rest of the mold. During application of 'heat and pressure tothe mold for .moldingthe backing plate 1 to the body 2 or '13, intheusual 7 manner, the "abrasive portions 8, 9 or 15,16, as .thecase mayhe, will be formed andmolded integrally with the body? orf13,respectively.

Summary It will now be seen that the improved brake shoe, in

either of its embodiments will condition the wheel for a restrictedperiod of use following initial installation. With the first embodiment,in which only a part of the entire wheel-engaging surface initiallycontains abrasive material, a relatively light abrasive action will beeffected over a relatively long period, and then when the abrasivematerial is completely expended, composition brake material devoid ofsuch abrasive material will work upon a' Having now described theinvention, what I. claim new and desire to secure by Letters Patent, is:

'1. A brake shoe comprising a body having aplurality of segments joinedto a common backing portion having a generally convex surface at theside thereof opposite to said segments, said segments having respectivearcuate surfaces adapted for engagement with a rotatable member to bebraked, the segments adjacent opposite arcuatctends of said bodycomprising abrasive material for a depth .of a fraction of an inch asmeasured from their respective arcuate surfaces toward said convexsurface, and the remainder of said body being composed of a materialother than said abrasive material.

2. A :brake shoe body comprising a backing portion having a generallyconvex surface and a plurality of segments joined to said backingportionat :the opposite side thereof from said convex surface, said segmentshaving respective-surfaces which are adapted for engagement with arotatable -member to be braked and are disposed in arcuate alignmentwith each other and opposite fto :sa'id backingportion, the outersegments farthest from .each other each comprising a portion containingabrasive material, .the latter portion being a fractionof the :totalthickness of the respective segment as measured from the correspondingarcuate surface to said backing portion and the segments intermediatesaid outer segments and remaining part of said outer segments beingcomposed solely .of composition brake material.

References Cited intthe file of this patent UNITED STATES BAZIIENTS1,1674937 Sayre Jan. 11,1916 1,369,497 Thompson Feb. 22, 1921 1,547,190Zabinski July 2 ,1925 2,261,191 Matthews May '21 I940 aifteen n.

1. A BRAKE SHOE COMPRISING A BODY HAVING A PLURALITY OF SEGMENTS JOINEDTO A COMMON BACKING PORTION HAVING A GENERALLY CONVEX SURFACE AT THESIDE THEREOF OPPOSITE TO SAID SEGMENTS, SAID SEGMENTS HAVING RESPECTIVEARCUATE SURFACES ADAPTED FOR ENGAGEMENT WITH A ROTATABLE MEMBER TO BEBRAKED, THE SEGMENTS ADJACENT OPPOSITE ARCUATE ENDS OF SAID BODYCOMPRISING ABRASIVE MATERIAL FOR A DEPTH OF A FRACTION OF AN INCH ASMEASURED FROM THEIR RESPECTIVE ARCUATE SURFACES TOWARD SAID CONVEXSURFACE, AND THE REMAINDER OF SAID BODY BEING COMPOSED OF A MATERIALOTHER THAN SAID ABRASIVE MATERIAL.